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µBITX ... AGC or AVC? an interesting article by Curt WB8YYY ... maAgain,e that's the solution to my troubles ! #ubitx #bitx40 #bitx20 #v6 #ubitxv6


Jack, W8TEE
 

Again, I'm not an EE type, but if the metering is done off the volume control, is it really an SWR meter or a VU meter??

Jack, W8TEE

On Wednesday, October 28, 2020, 12:49:45 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:


This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however.

Bob — KKR

Inline image


On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:


On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR

--
Jack, W8TEE


Bob Lunsford
 

The signal off the volume control can be used as a signal source for either S-meter purposes OR a way to control an AGC circuit by causing attenuation for signals above a pre-set level. However, I learned with my G90 that there are times when the AGC should be shut off to provide maximum signal gain.

Bob — KK5R

On Wednesday, October 28, 2020, 12:56:25 PM EDT, Jack, W8TEE via groups.io <jjpurdum@...> wrote:


Again, I'm not an EE type, but if the metering is done off the volume control, is it really an SWR meter or a VU meter??

Jack, W8TEE

On Wednesday, October 28, 2020, 12:49:45 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:


This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however.

Bob — KKR

Inline image


On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:


On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR

--
Jack, W8TEE


Arv Evans
 

Bob and Jack

Seems that if you are using that circuit and an ADC input in place of an analog 
meter, you could use software to convert the ADC readings into VU meter, 
S-meter, or anything else.  Might be a way to show Peak readings versus 
Average, and even to calculate receiver input in Microvolts.

Arv
_._


On Wed, Oct 28, 2020 at 11:26 AM Bob Lunsford via groups.io <nocrud222=yahoo.com@groups.io> wrote:
The signal off the volume control can be used as a signal source for either S-meter purposes OR a way to control an AGC circuit by causing attenuation for signals above a pre-set level. However, I learned with my G90 that there are times when the AGC should be shut off to provide maximum signal gain.

Bob — KK5R

On Wednesday, October 28, 2020, 12:56:25 PM EDT, Jack, W8TEE via groups.io <jjpurdum=yahoo.com@groups.io> wrote:


Again, I'm not an EE type, but if the metering is done off the volume control, is it really an SWR meter or a VU meter??

Jack, W8TEE

On Wednesday, October 28, 2020, 12:49:45 PM EDT, Bob Lunsford via groups.io <nocrud222=yahoo.com@groups.io> wrote:


This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however.

Bob — KKR

Inline image


On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:


On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR

--
Jack, W8TEE


Jack, W8TEE
 

Agree.

Jack, W8TEE

On Wednesday, October 28, 2020, 3:12:56 PM EDT, Arv Evans <arvid.evans@...> wrote:


Bob and Jack

Seems that if you are using that circuit and an ADC input in place of an analog 
meter, you could use software to convert the ADC readings into VU meter, 
S-meter, or anything else.  Might be a way to show Peak readings versus 
Average, and even to calculate receiver input in Microvolts.

Arv
_._


On Wed, Oct 28, 2020 at 11:26 AM Bob Lunsford via groups.io <nocrud222=yahoo.com@groups.io> wrote:
The signal off the volume control can be used as a signal source for either S-meter purposes OR a way to control an AGC circuit by causing attenuation for signals above a pre-set level. However, I learned with my G90 that there are times when the AGC should be shut off to provide maximum signal gain.

Bob — KK5R

On Wednesday, October 28, 2020, 12:56:25 PM EDT, Jack, W8TEE via groups.io <jjpurdum=yahoo.com@groups.io> wrote:


Again, I'm not an EE type, but if the metering is done off the volume control, is it really an SWR meter or a VU meter??

Jack, W8TEE

On Wednesday, October 28, 2020, 12:49:45 PM EDT, Bob Lunsford via groups.io <nocrud222=yahoo.com@groups.io> wrote:


This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however.

Bob — KKR

Inline image


On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:


On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR

--
Jack, W8TEE


--
Jack, W8TEE


Bob Lunsford
 

Right Arv ... Software is the way to go. Otherwise someone is being amazed by flashing lights and bird whistles. This is just one opinion, however.

Bob — KK5R

On Wednesday, October 28, 2020, 3:12:56 PM EDT, Arv Evans <arvid.evans@...> wrote:


Bob and Jack

Seems that if you are using that circuit and an ADC input in place of an analog 
meter, you could use software to convert the ADC readings into VU meter, 
S-meter, or anything else.  Might be a way to show Peak readings versus 
Average, and even to calculate receiver input in Microvolts.

Arv
_._


On Wed, Oct 28, 2020 at 11:26 AM Bob Lunsford via groups.io <nocrud222=yahoo.com@groups.io> wrote:
The signal off the volume control can be used as a signal source for either S-meter purposes OR a way to control an AGC circuit by causing attenuation for signals above a pre-set level. However, I learned with my G90 that there are times when the AGC should be shut off to provide maximum signal gain.

Bob — KK5R

On Wednesday, October 28, 2020, 12:56:25 PM EDT, Jack, W8TEE via groups.io <jjpurdum=yahoo.com@groups.io> wrote:


Again, I'm not an EE type, but if the metering is done off the volume control, is it really an SWR meter or a VU meter??

Jack, W8TEE

On Wednesday, October 28, 2020, 12:49:45 PM EDT, Bob Lunsford via groups.io <nocrud222=yahoo.com@groups.io> wrote:


This again is offered to show an S-meter circuit borrowed from the transceiver circuit being sold from Indonesia. It is apparently attachable to the volume control and since it's in the receive system, it does not affect the transmit system. It can be "rubbered" here and there since the component values may be the best for this considering that they are what is available to the builders in Indonesia, the FET and transistor can work equally well when using substitutes. Attaching to the high end of the uBITX's volume control and making the 47K variable in the circuit below a set resistor for calibration purposes results in making this a usable circuit. The meter, of course, can be substituted with an LED barcode circuit OR merely provide a source signal for an on-screen display of received signal level. The circuit as shown is relatively simple, however.

Bob — KKR

Inline image


On Wednesday, October 28, 2020, 7:06:58 AM EDT, IW4AJR Loris <lorisbollina@...> wrote:


On the CCARC (Carroll County Amateur Radio Club, Inc.) website I found a very interesting article on automatic gain control that is worth reading!
Without many frills Carol makes us understand that an AGC (automatic gain control) on the IF of the uBITX, due to the nature of the amps used (bidirectional), is very complex to make at this level of the circuit ...
therefore ? ...
Much better and less invasive to act directly on the volume control, implementing a simple but effective automatic volume control (AVC)!
Think man ... think ...
A little less software and a little more electronic experimentation and, with much less effort, very complex problems can be solved!
Think man ... think !
Greetings to all, Loris IW4AJR

--
Jack, W8TEE


Curt
 

It is certainly neither!  The meter fidelity wasn't a key objective except I needed to feed something to the panel meter on my imported case.  I am curious how some high end ubitx circuits are getting a log type S-meter behavior (is the amplitude linear sensed and the log in the computing math?). 

The AGC behavior in gently reducing large signals is my AGC interest.  I need to examine the actual built circuit hopefully tomorrow.  I remember VK3YE had a mistaken resistor value that I copied into my schematic - even though I corrected it in my build.  I think it is the base resistor feeding the second transistor, closest to the LED - seems my board may have 560 ohms here a huge change.  As I added some parts for the meter function - it will take a little time to unravel my board.  As this circuit is rather simple and it does the function, I recommend considering and trying it - but expect some experimenting around the particular LED and LDR you possess. 

73 curt wb8yyy


 

Hello Jack,
from the volume control you can only read a VU-meter, to have a real S-meter it is essential to take the medium frequency signal and treat it properly, instead, to read the SWR or better to say the "standing waves" in transmission, It is essential to insert a "directional coupler" in series between the TX and the antenna to obtain the two values of direct power and reflected power and relate them through a specific formula.
Hi de, Loris IW4AJR


Curt
 

Loris

You are correct in these statements, that signal strength must be measured independent of the volume control, meaning we cannot sample it after the volume control setting. Second that rendering a specific S level involves specific math.

I get less concerned about absolute calibration because our antennas are not the same. I don't know if my commercial HF rig has its S meter is calibrated based upon signals into a free space dipole. Okay folk with accurate signal generators can know. The relative difference of 6 dB per S unit seems more vital, especially over small ranges.

Cool stuff this radio science. Great it can be experienced with the ubitx and other home constructed transceivers.

As for accurate relative measurements,  there are nice log detector chips available.

Everyone should keep thinking but also to catch a wave with your receiver, and make a wave with your transmitter.

73 to all here

Curt